AS THE EXAMPLE of Illinois Gov. Rod Blagojevich (D) illustrates in profane, sickening detail, you can't legislate morality. But you can reduce the opportunities for temptation. Illinois offers useful guidance on how to accomplish that.

Politics is inevitably a business of horse-trading, back-scratching and favor-banking. That's a fact of life, and not necessarily a lamentable one. The art of the possible requires compromise. The biggest problem arises when the relentless demand for campaign contributions becomes part of that mix. The simplest solution would be to eliminate that piece of calculation -- and temptation -- by providing for public financing; it is no coincidence that Sen. Richard J. Durbin (D-Ill.) has championed such a measure in Congress.

Short of that step, however, every jurisdiction that does not have these rules should immediately consider: capping the size of campaign contributions; barring contributions from anyone but individuals and regulated political action committees; excluding donations from those who have or are seeking contracts or other business with the state or other entity; tightening disclosure rules so that limits are not easily sidestepped; and beefing up enforcement to provide effective, and timely, results.

Illinois is, for the most part, an example of what not to do. It has no limits on the size or source of campaign contributions -- a recipe for corruption spelled out in precise detail in the Blagojevich complaint. The state has just enacted a law -- over Mr. Blagojevich's veto -- prohibiting "pay to play" contributions. Contractors with state business worth more than $50,000 will not be allowed to make donations to officeholders with power to award such goodies. This important, if imperfect, change allegedly spurred Mr. Blagojevich to scramble for big checks before the law was to take effect Jan. 1. In one of the more pungent such instances, Mr. Blagojevich is described as saying of Children's Memorial Hospital, "I'm going to do $8 million for them. I want to get [Hospital Executive 1] for 50" -- an apparent reference to his desire for a $50,000 contribution in return for his commitment to help the hospital obtain state funds.

But the law would still allow canny donors to give money to other political committees to funnel to the politician, and lawmakers who can exert influence on the awarding of contracts are not covered by the ban. Meanwhile, disclosure rules are lax; for instance, contributions raised during the legislative session do not have to be reported until months later. Illinois' system of enforcing campaign finance laws makes the Federal Election Commission look robust; a maximum penalty of $10,000 offers little deterrence.

It's easy to look at Mr. Blagojevich's downfall, not to mention the similar fate of three of his recent predecessors, and ask: What's the matter with Illinois? But it's not just Illinois. The seamy story should prompt a reexamination at every level of government about whether enough has been done to preclude similar scandals.